Pump



Jan. '8, 1952 Filed March '7, 1946 H. E. ADAMS 2,581,828

PUMP

2 SHEETSSHEET l FLgl Wags

H. E. ADAMS Jan. 8, 1952 PUMP 2 SHEETSSHEET 2 Filed March 7, 1946 21Figfi. flux! 2, d M

lPatented Jan. 8, 1952 UNITED STATES PATENT OFFICE PUMP Harold E. Adams,Norwalk, Conn., assignor to Nash Engineering Company, South Nor-walk,Conn., a corporation of Connecticut Application March 7, 1946, SerialNo. 652,633

21 Claims.

The present application is a. continuation in part of application SerialNo. 493,662 now Patent Number 2,461,865, and deals with an inventionrelating to the pumping of highly volatile effervescent or glass-ladenliquids, such as gasoline, when pumped, for example, from aircraft fueltanks to engine carburetors.

In the parent application referred to, there is described as a specificapplication of the invention a fuel booster centrifugal pump mounteddirectly on the-bottom of or inside of the fuel tank, to deliver fuelunder pressure to the main engine fuel pump. In order to prevent vaporlock, the fuel pump has associated therewith a gas removal pump, and thetwo pumps are so associated and constructed as to deliver bubblefreeliquid fuel to the main engine fuel pump.

One object of the present invention is to provide a new and improvedpump unit comprising a centrifugal liquid pump and a gas removal vacuumpump constructed and arranged to afford efl'ective gas purging action,and to handle a large quantity of fuel by means of a small compact unit.

In accordance with the present invention, the centrifugal liquid pumphas a gas collecting annular chamber or groove communicating with theliquid pump chamber, and encircling the inlet of said liquid pump nearthe suction end thereof. The entrained gas in the centrifugal pump iscentripetally separated from the liquid, collected in said annularchamber, and then conducted to the inlet of the gas removal pump.

One of the features that distinguishes the centrifugal impeller of thepresent invention from the conventional one is the extreme height orwidth of the impeller blades at the entrance to the impeller wheel, ascompared with the height at the exit. This results in an angle of about35 between the conical side or end of the impeller and its axis ofrotation as compared with the normal impeller wheel angle 75 to 80. Thepurpose of providing a pump with these extreme proportions is to slow upthe liquid as it enters the field of operation of the impeller blades tothe point where suflicient time will be allowed during the passage ofthe liquid from the entrance to the exit of the impeller wheel to permitthe free gas or vapor carried y the liquid, to separate out bycentripetal action and concentrate around the inner diameter of thewheel, where it may be drawn in by the annular gas collecting groove orgrooves, and conducted by the suction connections to the gas removalvacuum pump. This blade dimen- 2 sional feature serves not only to slowdown the liquid being pumped, so that a more effective gas separatingaction is afforded, but also serves to maintain the liquid under astatic head during 'its passage through the impeller, so that theflashing of the liquid into vapor is reduced to a minimum.

In designing the entrance angles of the impeller blades, carefulconsideration is usually given to the calculation of entrancevelocities, so that the liquid flows into the field of action of theseblades with a minimum of disturbance. In other words. the entrance angleof the blades is usually designed so that the blades follow as closelyas possible the lines of flow of the liquid entering under the givenvelocity and entrance area conditions.

Another characteristic rule usually followed in the design of animpeller is that the velocity of flow of the entering liquid startingfrom rest in the pool of liquid above the pump must be graduallyaccelerated after it passes the entrance of the pump in a constantlyincreasing amount until it finally leaves the exit end of the impellerat its full discharge velocity as imparted to it by the impeller blades.There has been noexception to this rule, the velocity .being acceleratedfrom the entrance immediately adacent the impeller wheel or eye, as itis generally called, through the entrance of the impeller bladesthemselves, the liquid being accelerated during its entire passage inthe field of operation of the blades.

In accordance with the present invention, however, the liquid pump isdeslgned so that the liquid after entering the eye of the pump,immediately adjacent to the pump blades, is decelerated rather thanaccelerated as it is picked up by the'entering blades of the impeller,the entrance velocity of this liquid through this eye being in additionlower than the velocities of the liquids in conventional pumps handlingliquids near the boiling point.

- A pump of good impeller design for boiling liquid has previously beenconsidered one having velocities at the impeller eye of the order offrom 5 to 8 feet per second, with velocities ahead 01 this ranging downto 3 feet per second, whereas in accordance with the present invention,the impeller is designed to afford velocities at the eye desirablyranged from 2 to 5 feet per second. After the liquid enters the impellerblades, there is still a greater difference in the characteristicsbetween the impeller of the prior art and that of the present invention.In the case of the impeller of the present invention, the velocities atthe entrance to the impeller blades desirably drop to a low value of 1to 2 feet per second, whereas in the convential impeller, thesevelocities increase from 5 to- 15 feet per second.

There is another basic diflerence .in t.he entrance angle of the bladesin the impeller of the present invention as compared with that of theconventional type. As indicated above, the impeller blades of the priorart generally are proportioned so as to meet the entering stream ofliquid with a minimum of shock, the blade angle being determined bycalculation of flow velocities in conjunction with impeller areas andcapacities dealt with. In accordance with the present invention,however, the entrance angles of the impeller blades are designed tohandle a volume of flow three or four times the volume of liquid to behandled by the impeller so that volume of gas which is three or moretimes the volume of liquid discharged from the outlet ends of theimpeller blades. a

The designing of the pump to handle .a large proportion of gas and vaporat, the entrance ends, of. the impeller blades, whether or not these gasand vapor proportions are present. takes care of those excessiveproportions of gas to liquid when they do occur, and although whenhandling substantially gas-free liquid theremay be present shockconditions resulting-from the fact that theblades are dimensioned tohandle three times this quantity of liquid, the otherwise detrimentaleifect of this shock is offset by the slow velocity of the liquidthrough the impeller, affording ample timefor centrifugal-separation,for condensation of the vapors flashed by the entrance shock conditions,and for concentration of any non-condensible gases, holdingthem near thecenter of the impeller, where they can be withdrawn through the annularcollecting chamber by a suitable vacuum pump connection..

As another feature ofthe present invention, the pump affords relativelylong-flow passages from the entering edges of the impeller .blades' tothe exit ends thereof. If the liquids were allowed to freely acceleratebetween the entrance and the exitv by the action of centrifugal force,it would .take about. one-quarter of a revolution of the impeller toeffect this transltion.

. In accordance with the present invention, the pump is constructed tohold back the liquid in the impeller ,for approximately three come pleterevolutions from 'the' time it passes .the entrances of the bladesuntil.it leaves the exits. By thus holding back-the liquid and retaining. itinthe-passages of.the impeller for three Coma plete revolutions, thereis provided. ample-time for the .complete separation of gases and-vaporsfrom the liquid portion of the mixture entering the pump, and for thesegregationflof the. gas at the inner-diameter, where, asindicatedabove, it maybe removed by the vacuum-pump,

-Asanother feature ofthe present invention,

the liquid centrifugah pump -i s of the double suction impeller type,having two annular'gas collecting grooves for the two respectiveimpeller sections, these gas collecting grooves being served byindependent suction conduits, each conduit in turn having an independentsuction port to a liquid ring gas removal suction pump. This liquid ringsuction pump is of two-lobe construction, allowing each lobe to operateindependently of the other as far "as its suction connections areconcerned, so that each lobe draws vapors and gases from one annularcollecting groove, and the other draws vapors and gas from the othercollectinggroove. Since these two lobes are independent of each other,this construction is the equivalent of two separate vacuum pumps drawingfrom two separate annular gas collecting grooves independent of eachother. This feature of independent lobes with separate suctionconnections is important. because if the suction conduits of bothannular grooves were joined together 'before they entered acommon'vacuum pump, one or the other of the suction conduits leading tothe respective annular groove would take more of its share of the totalvacuum 'pump capacity at the expense of the other suction conduit. Inother words, the suction of the vacuum pump would take the line of leastresistance, and it would draw through the annular collecting groove thathad the least resistance at the expense of the other annular groove. Byseparating the two; and connecting each suction conduit to itsindependent vacuum pump, there is attained full surface for each of theannular gas collecting grooves, regardless of the condition of the othergroove.

\ Various other objects, features and advantages of the invention willbe apparent from the following particulardescription, and from aninspection of the accompanying drawings, in

which:

Fig. l is a longitudinal section of a pump unit embodying the featuresof the present invention;

Fig. 2 is a section taken on line 2-2 of Fig. 1;

Fig. 3 is a plan section taken on line 3-3 of Fig. 1,, and showing thetwo-lobe construction of the vacuum pump with two portions of the rotorbroken away to show the separate inlet passages therefore;

Fig. 4 is a plan section taken on line 4 -4 of Fig. 1, and showing theoutlet port on the top of the lobe casing, one portion of the lobe cas-jing being broken away to show the bottom inlet port; and v v Fig. 5 is aperspective of the impeller.

Referring to the drawings, the pump assembly, of the present inventionis shown of the fuel submerged typedesigned'for mounting on the bottomor lower sideof an aircraft. fuel tank, andadaptedto be securedtothebottom wall of said tank by a mounting fiangelll forming part ofsaidassembly. jTheupumping assembly comprises a booster.centrifugaluliquid pump ll having a centrifugal impeller l2 mountedatthe lower .end of ayertical shaft l3l'which. isdriven from .an electric,motor. enclosed-in a liquid tight casing .il anda gas removal ;vacuumpump 44 with a ro'torlll mounted on-said shaft.

-. j The. complete pumping a'ssen'ibly is 'securedfm position withrespect t -the-fueltankv to afford, free gravity flow. of. theliquidfuel from the .tank into the" pumpsectiom For that purpose,thecentrifugal liquid pump I I is enclosed in a pas-.5 ine- 1 3 w al -out h'-w U a 2 the p er n1et9 d-;. lf hi communication with the bottom of thefuel tank, and is covered with a strainer t8, while the lower section ofsaid well communicates with bottom suction side 3| of the pump II. Thetop suction side 32 of the pump ll communicates with the bottom of thefuel tank through a strainer 94.

The liquid fuel is discharged from the centrifugal impeller l2 through acollecting volute and a discharge nozzle 26. Suitable flexible hoseconnections are made at this point to the fuel line leading to the mainengine fuel pump outside the fuel tank.

In order to afford greater pumping capacity with a unit of minimum size,the liquid pump ll is of the double-suction type comprising a combinedwheel hub and web'2'l secured to the lower end of the shaft l3 forrotation therewith,- and having afilxed thereto on opposite sidesthereof two sets of impeller blades or vanes 29'and 29. "and 29have'respective axial eyes or suction openings 3| and 32, to which theliquid flows on its way to the inlet ends 33 of the corresponding set ofimpeller blades.

- The highly volatile and ebullient liquid flows by gravity through thestrainers l9 and 64 to the suction eyes 3| and 32 respectively. With thestrainers I9 and 64 located above these suctioneyes 3| and 32, some ofthe bubbles entrained in the liquid may have an opportunity to risecounter to the slow downward flow of liquid, and thus escape to thesurface of the fuel in the tank. Some of these bubbles, however, areentrapped with the liquid passing through the eyes 3i and 32 of theimpeller l2, and will be engaged by the leading edges 33 of the'impellerblades 28 and 29.

32 with the entering liquid, there will be bubbles evolved when thevolatile liquid strikes the revolving leading blade edges 33.

The presence of air or gas bubbles in any appreciable volume will breakdown the action of a centrifugal pump. This is due to the lowering ofthe average density of the fluid in the impeller by the presence of thegases and vapors, with the result that sufllcient head cannot begenerated by the impeller to fulfill its normal discharge headrequirements.

The impeller pumping rate diminishes approximately as the over-alldensity of the fluid in the impeller is reduced by the presence ofbubbles, and it may continue to reduce to a point where all pumpingceases at a given head. In

the case of the aircraft application, the delivery of bubbles in themain engine fuel pump suction is detrimental to the latters pumpingaction, and the mere presence of the bubbles alone may cause failure ofthe main engine fuel pump before the actual reduction in pumping volumeof the fuel booster pump occurs. In accordance with the presentinvention, continuous separation, collection and removal of thesebubbles from the passages of the impeller is effected, so that thedensity of the liquid therein will be suilicient to insure flow and fulloperation of the centrifugal pump.

.The centrifugal blades 29 and 2-9 are arranged and constructed to setup a circulating movement within the passageway defined between eachpair of adjoining blades in addition to the radial flow therethrough.When gas bubbles are entrained in the liquid being pumped; these bubblesare urged towards the leading edges .33

These two sets of impeller blades In addition to the bubbles alreadycarried from the eyes 3| and by this circulating movement, and by theaction of differential presure between the adjoining blades. There isalso the effect of centrifugal force tending to separate the gasbubbles. and to force these bubbles centripetally towards the centerportion of the impeller l2, while at the same time allowing the moresolid liquid to pass radially outwardly along the pressurized leadingface of each impeller blade 28 or 29. The result of these forces is aconcentration of separated gas near the entrance of each impellerpassageway.

Means are provided for withdrawing this accumulated gas. For thatpurpose, the pump casing l5 has a lower annular collecting groove 36near its radially irmermost side in communication with the impellerpassageways defined by the lower set of blades 29, and an upper annularcollecting groove 37 disposed near its innermost radial side of thecasing, and in communication with the impeller passageways defined bythe upper set of impeller blades 29. The lower annular gas collectinggroove '36 opens up into a gas take-off or suction conduit 40, 4| and42, leading to an inlet port 43 in a vacuum gas removal pump '44. Theupper annular gas collecting groove 31 opens into a gas take-off orsuction conduit 45 leading to another inlet port 490i the vacuum gasremoval pump 44.

The gas removal vacuum pump 44 is of the liquid ring type, and comprisesa rotor- 41 secured to the shaft l3 for rotation therewith, and enclosedin a casing 48. The pump is of the two-lobe type, the separate lobes ordisplacement chambers in the pump being indicated at their deepestportions as and 5|.

The gas from the pump is discharged from the vacuum pump 44 throughupper ports 52 and 53 in the pump to a gas discharge chamber 54, andthis gas is then discharged through a port 55 into the tank or source ofsupply.

The gas centripetally accumulated within the confines of the impellerpassages is drawn off by the suction action of the auxiliary gas pump 44at a rate equal to the formation or accumulation of gas in this region.

The inlet port 43 of lobe 50 derives its suction through conduits 42, 4|and 49, removing air and vapor collected in the bottom collecting ringor groove 3'5, .and this lobe 50 discharges vapors collected from thisbottom collecting groove through its discharge port 52, where it in turndischarges into the common discharge chamber 54, and thence through thedischarge port 55 to the tank. The other inlet port 45 of lobe 5|derives its suction through the conduit 45, and removes vapors and aircollected in the upper annular groove 31. -The discharge from this lobe5| is through discharge port 53 into the common discharge chamber 54through the port 55, and into the tank or source of supply.

It should be noted that the two lobes 59 and 5lform separate pumpingchambers with one common rotor 41, each chamber having its own inlet anddischarge port, so that each lobe operates independently of the otherasfar as their suction connections are concerned. By separating thesesuction connections, there is provided the equivalent of separateindependent vacuum pumps for each side of the double-suction pump.

I thus obtaining definite removal of gas from each of the gas from oneside of the impeller at the expense of the other side.

As an additional feature of the present invention, the impeller blades28 and 29 at the entrance to the impeller wheel l2 are of comparativelyextreme width to slow up the liquid as it enters the field of operationof the impeller blades, sufliciently to permit the impeller blades toseparate centrifugally the free gas or vapor from the liquid and collectit in the annular collecting grooves 88 and 81. To slow up the liquid tothis extent, the axially open sides or ends 60 of the impeller describesubstantially conical surfaces of revolution about the axis of theimpeller shaft l8, each inclined 35 with re- 1 spect to said axis asindicated by the angle A in Fig. 1 compared with the usual impellerangle A of about 75 to 80. The impeller of the present invention thusforms. an included angle of about 110 between both conical surfacesdefined by of vapor and gas to liquid, and I do not wish to.

be limited to this specified angle. It might vary from 15 to or more andstill be within cer-, tain aspects of the present invention.

As another feature of the present invention,

the pump is proportioned so that the liquid after entering the suctioneyes 8| and 82 of the pump immediately adjacent to the impeller blades28 and 29, is decelerated rather then accelerated as it is picked up bythe leading edges of these blades. For that purpose, the cross-sectionalflow combined cross-sectional areas of the flow passages in the impellerwheel 12 along the full length of said wheel, and along the leadingedges 83 of the combined impeller blades 28 and 29 at the entrance tosaid passages. These areas are desirably proportioned so that thecombined cross-sectional areas at the entrance to the flow passages inthe impeller wheel 12 is about twice the cross-sectional vflow area ofthe suction eye 8| or 32. With such relative pump dimensions, and withthe pump operating at a desirable liquid flow velocity of 2 to 5 feetper second at'the suction eye 8|, the velocity of the liquid at theentrance to the impeller blades 28 and 29 drops to 5 a low value of l to2 feet per second.

As another feature of the present invention, the impeller blades 28 and29 are proportioned and designed to handle a volume of fluid flow attheir entrance end from about three to four times the volume of liquidto be handled by the impeller l2 at its exit end.

The reason for this departure in the proportioning of the impellerblades 28 and 29'from conventional design, is that the pump of thepresent invention is designed to handle fluids containing largequantities of previously entrained gasas well as gas evolved byshockconditions at the entrance to these blades. These impeller blades- 28and 29 are therefore proportioned to handle at their inlet a volume offluid three or more times the volume of liquid discharged into thevolute 25 from their exit.

The detrimental shock effect of this disproportionate entrance design,when the 'impeller is shock conditions, or separate and compressanygases or vapors which are diflicult-tdcondense and collectthem in theannular grooves 86 and 81 from which they can be withdrawn through theaction of the vacuum pump 44.

As another feature of the present invention, the pump is designed toaflord a relatively long length of time for the passage of the liquidfrom the entering edges 32 of the impeller blades 28 and 29 to theirexit edges. If the liquid were allowed to accelerate freely fromentrance to exit by the action of centrifugal force alone, it wouldtake-about $4; of a revolution of the impeller to complete this travel,and this is the usual value for the average conventional centrifugalpump impeller. In the present invention, due to the disproportionatedesign in-the impel: lerpassages, to handle at least three times the,quantity at the inlet that is provided for at the exit, this largerquantity .of liquid entering the impeller is slowed down in its passagefrom entrance to exit so that it. takes approximately. three completerevolutions from the time a particle of liquid passes the entrance ofthe blades to the time it leaves the exit. In addition to this feature,the impeller blades 28 and 29 have their radial outer sections 63extending. for substantial distances somewhat concentric with respect tothe axisof .the impeller l2 asshown in Fig. 2 and circularly, so thatthe extent of their radial components. at these outer sections isreduced to a minimum.

As'many. changes can be ,made in the aboveapparatus, and many apparentlywidely difler-t .5- nt embod men of area of the suction eye II or 82 isless than the e 1 ts this invention can be made" without departing fromthe scope of the claims. it is intended that all matter contained inthe: above description or shown in the accompany ing drawings shall beinterpreted as illustra- -l( tive and not in a limiting sense.

5 ant is set forth in the appended claims.

handling a clear liquid or approximately onecondense the vapors flashedby blade entrance? .charge connection to the said source of supply.-'

'2. A centrifugal pump comprising a c'entri-fugal impeller of thedouble-suction type, having two impeller sections with respectiveinlets, said pump having'anoutlet, a liquid pump chamberfor saidimpeller, and two annular gas collecting chambers communicating directlywith the in'-'- terior' of the liquid pump chambernear saidinlets.respectively, and extending around the axis'of rotation of saidimpeller, said pump having conduits for leading the collected gases awayfrom said gas collecting chambers. 4

'3; A centrifugal pump comprising "acentrifu-' gal impeller of thedouble-suction type, having two similar adjoining pumping sections withrespective inlets, and a casing enclosing said im-'-peller-and-having-two axially spaced annular gas collecting grooves,said-pump havingan' outlet,- and; a liquid pump chamber for saidimpeller, said grooves communicating" directly with the liquid .pumpchamber near said inlets respectively and-extending around the. axis-p!rotation of said impeller, and-pconduits tor-,leadilng-the gases awayfrom said grooves;

- .4. In combination. acentrifuBal liquid pump comprising aeentriiugahimpeller, of the double- 4 suction type having two similar acUoiningpump- :ing sections with' respective inlets, and a casing enclosing said.impeller .and having; two. axially spaced. annular, gascollectinggrooves. said pump having an outlet, and-a liquid-pumpchamberfor said impeller; said grooves. communicating di- .rectly with.the liquid pump chamber near said inlets respectively andextendins.around the axis 'ofrotation 01 said impeller. a gas removal pump,

.and conduitsbetween said grooves and, the inlet tions to said inletsrespectively;

6. The combination as described in claim ,5, in yvhichtheoutlet meansoisaid gas removal p ump comprises two separate outlets operativelycorresponding to said inlets respectively. v

7. {Thecombin'ation as described in claim 5 in which said gas removalpump is of the twolobesuctionrotary; type,- and said inlets extend intothe two lobe sections respectively of said latterpump.

8. T l e eombination as described in claim 5, in which the outlet meansof. said gas removal pump comprises two separate outlets operativelycorresponding tdsaid inlets respectively, said gas removal pump is ofthetwo-lobe suction-rotary type, .and-each of the lobe sections has acorresponding inlet and a corresponding outlet on the suction anddischarge sides respectively of said latter lobesection.

.9. In combinatioma pump having an outlet, and comprising a centrifugal,impeller for the double suction type having two similar adiq is pumpingsections with respective inlets,

and a casing enclosing said impeller and having a liquid pump chamberfor said impeller and two axially spaced annular gas collecting groovescommunicating with the liquid pump chamber near said inlets respectivelyand extending around the axis of rotation of said impeller, a gasremoval pump of the two-lobe suction type having two separate inletsleading to the two lobe sections of said latter pump respectively, andtwo separate outlets communicating with the two lobe sections of saidlatter pump respectively, and conduits connecting said grooves with saidlatter inlets respectively.

10. A centrifugal pump comprising a casing, an impeller therein definingwith said casing a plurality of liquid flow passages, the inlet andoutlet ends of said passages 'being proportioned to handle substantiallymore 01 the volume of the fluid at said inlet ends as at said outletends, said impeller having its blades with circumferential components ofsubstantial length which will cause the liquid in the pump during normalpumping operations to be retained in said passages for about threerevolutions or more of said impeller, the gas or vapor carried by theliquid passing through said passages being adapted to separate out fromsaid liquid and to concentrate in said passages at an' annular regionextending around the axis of rotation of said impeller and located nearand radially outwardly beyond the initial axial. entrance area to saidimpeller, means for collecting said separated gas or vaporatsaid'region, and means for drawing oi! said separated gas or vaporfrom said collecting means and away from the pump.

11. A centrifugal pump as described in claim 10, inwhich said impellerblades are curved substantiaily circularly for substantial distances atthe radially outer sections to retain the liquid inze pump during normalpumping operation for tieast one revolution of said impeller.

12. A centrifugal pump comprising a casing, an

- impeller therein defining with said casing a plurality of liquid fiowpassages, theinlet and outlet ends of said passages being proportionedto handle about three times the volume of fluid at said inlet ends as atsaid outlet ends, the gas or vapor carried by the liquid passing throughsaid passages being adapted LO separate out from said liquid and toconcentrate in said passages at a region around but near the innerperiphery oforawing 'off said separated gas or vapor from saidcollecting means and away from the pump, said collecting meanscomprising an annular collecting groove in saidcasing in directcommunication with said passages in said region, and said drawing meanscomprising a gas take-oil condult connected to said groove and leadingaway from the pump. i

13. A centrifugal pump comprising a casing, an impeller therein havingblades defining with said casing a plurality of liquid fiow passages,the width of said blades at their entrance end with respect to the widthat'their exit end and with respect to the cross-sectional area of theimpeller eye or inlet being such, as to slow up the liquid as it enterssaid passages and to create in said separated gas or vapor in saidregion defined by said casing, and conduit means for drawing off saidgas or vapor from said collecting chamber.

14. A centrifugal pump as described in claim 13, in which saidcollecting chamber is in the form of an annular groove on the inner sideof said casing communicating directly with said passages in said region.

15. A centrifugal pump comprising a casing, an impeller therein havingblades defining with said casing a plurality of liquid flow passages,the width of vsaid blades at their entrance end with respect to thewidth at their exit end being such as to create in said passages anannular region of lowest pressure or density extending around the axisof rotation of said impeller and located near and radially outwardlybeyond the initial axial entrance area to said impeller, an annularcollecting chamber for the separated gas or vapor in said region definedby said casing, and conduit means for drawing off said gas or vapor fromsaid collecting chamber.

a 16. A centrifugal pump comprising an impeller having rotary impellerblades mounted thereon, the outer edges of said blades on one sidedescribing a substantially conical surface of revolution about the axisof rotation of said impeller inclined approximately 15 to 45 withrespect to said axis, a casing for said impeller having its wallopposite said edges conforming close to said and located near andradially outwardly beyond the inlet of said impeller, means forcollecting said separated gas or vapor at said region, and means fordrawing the collected gas or vapor from said collecting means away fromthe pump.

17. A centrifugal pump of the double suction.

open impeller type, including an impeller whose' edges on each axiallyopen side describe a substantially conical surface of revolution aboutthe axis of rotation of said impeller inclined to 45 from said axis,thus forming an included angle between both conical surfaces of from 90to 150, a casing having walls closely conforming to said surfaces ofrevolutions and defining an inlet to said impeller, an outlet from saidimpeller, and a pump chamber therebetween, and means for separating thegas and vapor from the liquid in said pump chamber, collecting it, anddrawing it away from the pump.

18. A centrifugal pump comprising a casing, an impeller therein havingimpeller blades mounted thereon and defining with said casing a plurality of liquid flow passages through said pump, said pump having anoutlet and an axial suction inlet having an area in a plane at rightangles to the direction of flow therein substantially smaller than thecombined cross-sectional areas of said passages at their inlets, toeffect decrease in the velocity of the liquid as it passes from saidsuction inlet to said passage inlets, whereby sufilcient time will beallowed during the flow of the liquid through said passages to permitthe free gas or vapor carried by the liquid to separate out from saidliquid and to concentrate in said passages at an annular regionextending around the axis of rotation of said impeller and located nearand radially outwardly beyond the inlet of said impeller, means forcollecting said separated gas or vapor at said region, and means fordrawing oil said separated as or vapor from said collecting means andaway from the pump.

19'. A centrifugal pump as described in claim 18. in which said axialsuction inlet area and said combined passage inlet areas areproportioned about one to two. to decrease the velocity of the liquid toabout one-half as it passes from said suction inlet-to said passageinlets.

20. A centrifugal pump comprising a casing. an impeller therein definingwith said casing a pinrality of liquid flow passages, the inlet andoutlet ends of said passages being proportioned to handle about threetimes the volume of fluid at -said inlet ends as at said outlet ends,the, gas or vapor carried by the liquid passing through said passagesbeing adapted to separate out from said liquid and to'concentrate insaid passages at an annular region extending around the axis of retationof said impeller and located near and radially outwardly beyond theinlet of said im-' peller, means for collecting said separated gas orvapor at said region, and means for drawing oi! said separated gas orvapor from said collecting means and away from the pump.

21. A centrifugal pump as described in claim 20, in which means areprovided for retaining the liquid in the pump during normal pumpingoperations for at least one revolution of said impeller.

HAROLD E. ADAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,780,679 Jennings Nov. 4. 19301,901,154 Durdin Mar. 14, 1933 1,989,061 Longenecker Jan. 22, 19352,134,686 De lancey Nov. 1, 1938 2,368,528 Edwards Jan. 30, 19452,368,530 Edwards Jan. 30, 1945 2,402,398 Harpster June 18. 19462,461,865 Adams Feb. 15, 1949

